The present invention relates to a check valve of a scroll compressor used for refrigeration and air conditioning.
The operating principle of a scroll compressor is known from, for example, U.S. Pat. No. 801,182.
FIGS. 3A to 3D illustrate the basic principle behind the known scroll compressor. A crescent-shaped compression chamber 11 is defined by a fixed scroll 1 and an orbiting scroll 2. When the orbiting scroll 2 undergoes its orbiting motion, the volume of the compression chamber 11 gradually decreases as shown from FIG. 3A to FIG. 3C. In the state shown in FIG. 3C, the compression chamber 11 communicates with a discharge port 22 provided at a central portion of the fixed scroll 1. In the process illustrated from FIG. 3C to FIG. 3D, compressed refrigerant is discharged. In the known scroll compressor in which the refrigerant is compressed, it is possible to prevent the refrigerant from leaking from the compression chamber 11. Meanwhile, the known scroll compressor does not require a delivery valve in contrast with a reciprocating compressor and a rolling piston type of compressor and thus, is less noisy than such compressors.
However, in the known scroll compressor having no delivery valve, the orbiting scroll 2 is urged in reverse at a high speed due to a rapid back-flow of the refrigerant from a high-pressure side to a low-pressure side when the scroll compressor is stopped, such that abnormal noises and damage to its components may be incurred. In order to eliminate such potential problems, a device for preventing reverse movement of the orbiting scroll 2 must be provided.
Devices for preventing reverse movement of the orbiting scroll 2 are disclosed in, for example, Japanese Patent Publication Nos. 56-28237 (1981) and 1-34312 (1989). These devices are shown in FIGS. 9 and 10, respectively. In the former prior art device, a delivery valve 58 acting as a check valve is provided over a discharge port 22 located at a central portion of a fixed scroll 1 so as to prevent back-flow of refrigerant from a discharge space to a compression chamber when the compressor is stopped. This prior art document mentions that loss at the time of discharge can be prevented by this arrangement. However, in this arrangement, since the delivery valve 58 closes at the end of each rotation of a driving shaft 6, noises due to the striking of a valve seat by the closing delivery valve 58 are produced.
Meanwhile, in the latter prior art device, a valve 59 acting as a check valve and supported by a spring 26 is fixed to one end of a suction port 25 provided at the periphery of a fixed scroll 1 so as to prevent a back-flow of refrigerant. This prior art document acknowledges that the flow of oil out of a compressor can be prevented when the compressor is stopped. However, since the check valve is provided at the suction side, i.e., a low-pressure side, a back-flow of the refrigerant in an amount corresponding to the volume of space between the check valve and a discharge port takes place and thus, reverse movement of the orbiting scroll due to a back-flow of the refrigerant cannot be prevented completely. Furthermore, this check valve has a complicated structure.
Therefore, there is a demand for a check valve having a simple structure, and which not only positively prevents reverse movement of a orbiting scroll due to back-flow of refrigerant but also produces little noise.
To this end, a check valve shown in FIG. 4 was previously proposed by the present inventors and was placed on the market. In this device, a tube 23 for receiving a check valve 4 is provided on a discharge port 22 of a fixed scroll 1, and a valve retainer 5 for preventing the check valve 4 from being detached from the tube 23 is mounted on the tube 23. FIG. 11 shows the check valve 4. As shown in FIG. 11, the check valve 4 has the shape of a cross in which a plurality of legs 45 protrude from an outer periphery of a disk 41. In this conventional check valve device, since the check valve 4 is pressed against the valve retainer 5 by refrigerant, noises due to a striking of a valve seat by a check valve as in a delivery valve are not produced. However, rotation or chattering of the check valve 4 due to flowing refrigerant occurs according to various operational conditions, thus resulting in the production of noise. In particular, when the compression ratio, which is a ratio of high pressure to low pressure, rises, the refrigerant flows reversely in the vicinity of the check valve 4, thereby causing the check valve 4 to chatter.